Air-cooled internal combustion engine with soundproofing enclosure

ABSTRACT

An air-cooled internal combustion engine having a cooling air blower driven by the crankshaft and the soundproof enclosure surrounding the outer surface of the engine. A distributing chamber is provided in the cavity formed within the soundproof enclosure and cooling air is supplied by the blower inside the cavity and into the distributing chamber which from there passes over the cylinder cooling areas and various parts of the engine.

United States Patent Inventors Gerhard Thin;

Heinz Fachbach; Bernd Nowotny, all of Graz, Austria Appl. No. 824,899

Filed May 15, 1969 Patented Aug. 24, 1971 Assignee Hans Lkt Graz, Austria Priority June 6, 1968 Austria A5,433/68 AIR-COOLED INTERNAL COMBUSTION ENGINE WITH SOUNDPROOFING ENCLOSURE Primary Examiner-Mark M. Newman Assistant Examiner-Cort R. Flint Attorney-Watson, Cole, Grindle and Watson ABSTRACT: An air-cooled internal combustion engine hav- 6CMms9Drawingngs' ing a cooling air blower driven by the crankshaft and the US. Cl. l23/4l.70, soundproof enclosure surrounding the outer surface of the en- 181/334, 123/41.62 gine. A distributing chamber is provided in the cavity formed Int. Cl F0lp 1/02 within the soundproof enclosure and cooling air is supplied by Field of Search 123/4l.7, the blower inside the cavity and into the distributing chamber 195 C, 195 E,4l.66, 416141 62, 41.6]; which from there passes over the cylinder cooling areas and 181/334 various parts ofthe engine I 1 5 I 24 1 7 k \R \l o g2 II i K I \VN s i! a L 1 H i i ,1 1") i l/ 30 I 7 l Q on 1 26 1 l ll I i 28 ,44 4 i 7 7 PATENTEU mm m:

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sum 3 OF 4 AIR-COOLED INTERNAL COMBUSTION ENGINE WITH SOUNDPROOFING ENCLOSURE The invention relates to an air-cooled internal combustion engine with a soundproofing enclosure and a crankshaftdriven cooling-air blower.

Owing to the inadequate exchange of heat between the outer surface of the engine and its environment, the application of soundproofing casings to an internal combustion engine is invariably bound to produce higher wall temperatures and a corresponding increase in oil temperature, unless provision is made for the effective evacuation of excessive engine heat by means of an additional cooling system. However, this makes sense only as long as the additional power requirements involved in a more extensive cooling system are kept within economical limits and provided the additional noise produced by the blower does not offset the advantages resulting from such soundproofing.

Since former attempts at solving this problem failed to produce completely satisfactory results, it has been the object of the present invention to provide an internal combustion engine of the type hereabove described, ensuring both adequate soundproofing and substantially improved cooling conditions. According to the invention, the whole of the cooling air supplied by the blower is directed inside a cavity defined by the outer surface of the engine and the soundproofing enclosure into a distributing chamber and from there in separate branch currents over the cylinder cooling areas and the other components of the engine requiring cooling. Splitting the cooling air into a number of parallel-flowing branch currents offers a considerable advantage as compared with conventional arrangements featuring series-connected cooling-air ducts insofar as it is not necessary to increase blower pressure and furthermore, the blower impellers are not required to rotate at higher speed thus producing a substantially louder noisev In addition, it is possible to distribute the blower air and to determine the flow velocity of individual branch currents. in accordance with the cooling requirements of the various components of the engine.

The air supply of branch currents leading to points of lesser thermal stress can be throttled as required so that the amount of cooling air delivered by the blower will have to be increased to the absolutely necessary extent only, thereby keeping blower power requirements strictly within economical limits.

According to a preferred embodiment of the invention particularly suitable for use in connection with in-line engines, the cooling-air blower is mounted on the front or rear end of the machine in a laterally offset position, the distributing chamber adjoining the blower and extending alongside one sidewall of the crankcase, separate cooling-air ducts extending from the distributing chamber and leading to the cooling areas of the cylinder and cylinder heads, to the valve chamber housing and to the opposite sidewall of the crankcase, so as to provide adequate cooling for the crankcase wall adjoining the distributing chamber and through the connection to the opposite side of the engine also for the other crankcase wall in addition to the effective cooling of the cylinder and cylinder head areas of the engine. As a result, an objectionable oil temperature rise in the crankcase is positively avoided, it being even possible, under certain circumstances, by such means as the arrangement of cooling ribs in the bottom portion of the crankcase, to lower the engine oil temperature to such an extent as to render the provision ofa separate oil cooler superfluous, so that costs will be considerably reduced.

It is not necessary for the cooling-air passages leading to the cylinders and cylinder heads of the internal combustion engine to be designed as regular air ducts, since the cooling air passes from the distributing chamber through the vacant sectional areas between the ribbed cylinders and cylinder heads in appropriate branch currents to the other side of the engine. Where all of the cylinders are simultaneously supplied with cooling air, baffles can be installed in the distributing chamber in a manner known per se.

According to another feature of the invention, for the purpose of appropriately cooling both side of the crankcase, the

soundproofing enclosure covers also the bottom of the crankcase and/or the oil sump, and the intervening space between the bottom of the crankcase or the oil sump and the enclosure defines and air passage leading form the distributing chamber to the opposite sidewall of the crankcase. Thus the oil sump located below the crankcase is particularly included in the aircooling system, as a result of which the oil temperature is lowered considerably.

It is, however, also possible according to the invention, to provide for a passage connecting the distributing chamber with the space between the opposite sidewall of the crankcase and the portion of the enclosure in front of same, and extending transversely over the front end and/or the flywheel end of the crankcase. This arrangement is particularly suitable for internal combustion engines comprising a soundproofing oil sump. In that case, the soundproofing enclosure terminates approximately in the proximity of the oil sump connecting flange.

According to a further feature of the invention as applied to internal combustion engines comprising a cooling-air blower located at one end of the crankshaft, the cooling air is preferably directed from an inlet provided at the blower end of the engine alongside the walls of the crankcase to the suction end of the blower, and from the delivery end of the blower to the distributing chamber above, from where one cooling-air duct each branches off to the cooling area of the cylinder and of the cylinder headand to the valve chamber housing above. This is obviously a combination of the conventional series-connection of cooling-air ducts with the splitting of the cooling-air current into a number of parallel branch currents according to the invention, the entire cooling-air current which has been only moderately preheated in the area of the crankcase walls, being available at the delivery end of the blower in appropriate branch currents for the purpose of cooling the cylinder and cylinder head areas as well as of the valve chamber housing. Since the pressure drop of the cooling air drawn in through the intervening space between the crankcase and its soundproofing enclosure can be held at a very low level, it will not be necessary for the blower output to be substantially increased in spite of the series-connection of the cooling-air passages upstream and downstream of the blower.

According to a further feature of the invention, for the effective muflling of the high-frequency noise produced by the cooling-air current it is advisable to shield the air inlet and/or outlet in the soundproofing enclosure by means of a soundabsorbing housing placed in front of same. This housing may be included in the soundproofing enclosure of the engine or attached to it as a separate unit, provided the sound-absorbing section inside the housing does not fall short of a certain minimum length because sound-attenuation inside such a duct depends on its length, and further provided that the walls of these ducts are not of a sound-projecting nature such as are portions of the engine surface, for example. Furthermore, the width of the duct should not exceed the maximum required to ensure adequate sound-attenuation, and deflecting means should be provided in the housing in order to prevent the direct passage of high-frequency noise.

According to the invention, auxiliary machines such as the fuel-injection pump, dynamo, and the like, can be arranged in the cooling-air current inside the cavity defined by the engine surface and the enclosure. As a result, sound radiation from these auxiliary machines is blocked by the soundproofing enclosure and at the same time, the temperature of these machines is not allowed to rise unduly.

FIG. 3 a part-sectioned side elevation of the internal combustion engine illustrated in FIGS. 1 and 2.

FIGS. 4 and 5 show another embodiment of the invention,

FIG. 4 being a part-sectional view of the internal combustion engine on line IV-IV of FIG. 5, and

FIG. 5 a sectional view corresponding to FIG. 3.

FIGS. 4a and 5a show part-sectional views of the flywheel end of a variant of the internal combustion engine illustrated in FIG. 4 and FIG. 5, respectively.

FIG. 6 is a part-sectioned side elevation of an air-cooled single-cylinder internal combustion engine according to the in- -vention, and

FIG. 7 shows a horizontal section of this engine on line VII-VII of FIG. 6.

The internal combustion engine illustrated in FIGS. 1 to 3 comprises a soundproofing enclosure consisting essentially of the casings 1 and 2 located at the two sides of the engine, with a cowling 4 arranged below the oil sump 3 and another cowling 6 topping the valve chamber housing 5. The enclosure members 1, 2, 4 and 6 are attached to the corresponding wall areas of the internal combustion engine with the interposition of soundproofing spacers 7. The enclosure members are usually made from sheet steel, heat-resistant synthetic products and occasionally from multilayer sheets (sandwich sheets).

In conjunction with the outer surface of the crankcase 8, the oil sump 3 and the ribbed cylinder liners 9 together with the equally ribbed cylinder heads 10, the aforesaid enclosure members define an essentially coherent cavity sealed off from the outside. At the front end of the engine an axial flow blower 11 is provided which is laterally offset in relation to the longitudinal central plane of the engine and whose suction stub 12 is attached to the soundproofing enclosure at a front end aperture of same. The blower 1 1 is driven from the crankshaft ofthe engine by means ofa V-belt 13.

The blower 11 is preceded by a suction housing 15 whose inner surface is providedwith a sound-absorbing coating 16, and which, as appears in particular from FIG. 3, is provided with a deep-seated inlet 17. On the opposite side of the internal combustion engine an air-exhaust housing 18 is located, the inner surface of which is also lined with a sound-absorbing coating 16. A partition 19 of an approximately T-shaped cross section provided with a sound-absorbing coating divides the air exhaust housing 18 into two symmetrical air-outlet conduits 20, each comprising two deflections and terminating in an outlet 21. I

The cooling air entering the suction housing 15 through the inlet l7 is twice deflected and then arrives at the blower 11 from where it passes into the adjoining distributing chamber '2 defined by the enclosure member or casing 1 and the adiace .l lateral surface of the engine.

F i\ the distributing chamber 22 the cooling air, split up into a number of parallel branch currents, is directed to the component parts of the internal combustion engine requiring cooling. Four branch currents of about equal size enter the passages defined by the ribbed cylinders 9 and cylinder heads 10 between lateral shieldings 23 and pass on the other side of the engine through the two air-exhaust ducts and the outlets 21 into the open. Further branch currents enter the valve chamber housing 5 via throttle openings 24 on top of the cylinder head and also arrive at the air-exhaust housing 18 after passing appropriate overflow apertures 25.

Another branch current is directed between one sidewall 26 ofthe crankcase 8 and the casing l downwards and enters the intervening space between the oil sump 3 and its cowling 4 through a gap 27. Thus this cooling-air current first sweeps over the sidewall 26. then over the surface of the oil sump 3 and finally in an up-current also over the opposite sidewall 28 ofthe crankcase and the fuel-injection pump 29 ofthe internal combustion engine located between the sidewall 28 and the casing 2. Through a gap 30 this branch current also passes into the open via the air-exhaust housing 18. In addition to the fuel-injection pump 29, the starter 31 located within the enclosure in the distributing chamber 22 also comes into contact with cooling-air.

In the internal combustion engine illustrated in FIGS. 4 and 5, and FIGS. 4a and 5a respectively, the soundproofing enclosure ends at the connecting flange of theoil sump 3 on the crankcase 8; For the passage of cooling air from the distributing chamber 22 to the opposite sidewall of the crankcase 8, a connecting passage 32 extending transversely over the bottom of the suction housing 15 is provided as shown in FIGS. 4 and 5. This passage communicates via apertures 33 and 34 with the distributing chamber 22 on the one hand, and with the opposite space defined by the casing 2 and the sidewall of the internal combustion engine, on the other hand. In the embodiment of the invention illustrated in FIGS. 4a and 5a a connecting passage 32 is provided at the flywheel end of the casings 1 and 2 and communicates through apertures 33' and 34' with the aforementioned air-carrying spaces. The arrows in the drawings indicate the flow of cooling air within the visible portion of the enclosure.

The air-cooled single-cylinder internal combustion engine shown in FIGS. 6 and 7 comprises a cooling-air blower 35 located at the end of the crankshaft. The crankcase 36 together with the cooling-air blower 35 is surrounded by a multiple-part soundproofing enclosure 37 which in the embodiments of the invention referred to above is attached to the internal combustion engine with the interposition of spacers 7. Through two inlets 38 arranged symmetrically at the front end of the engine the cooling air first enters a downward passage 39 lined with a sound-absorbing coating and designed as a suction housing and, sweeping alongside the walls of the crankcase 36, arrives at the blower 35.

From the delivery end of the blower 35 the cooling air enters a distributing chamber 22 above, which is defined by the cylinder 40 together with the cylinder head 41 and an upper casing 42 surrounding these component parts of the engine.

From the distributing chamber 22' one cooling-air branch current each is directed over the cooling areas of the cylinder 40 and ofthe cylinder head 41. Another branch current passes through throttle apertures 43 into the valve chamber 45 covered by a cowling 44 and from there within a downward passage 47 defined by a vertical partition 46 to the fuel-injection pump 48. Through a gap 49 provided in the partition 46 this branch current of the cooling air rejoins the other branch currents directed downwards in the intervening space between the partition46 and the cylinder 40 and the entire exhaust air is evacuated into the open via an exhaust-air housing 50 mounted on the side of the cylinder and lined with a sound-absorbing coating 51, after having been deflected once, through an outlet 52.

A common feature of all embodiments of the invention hereabove described is the splitting up of the cooling-air current into a number of parallel branch currents the flow velocities and cross sections of which vary according to the coolingair requirements of the various component parts of the engine. This basic principle is obviously applicable to a number of different types of internal combustion engines.

I claim:

1. An air-cooled, soundproof internal combustion engine comprising a cooling-air blower driven by a crankshaft, with cooling surfaces on the cylinders and cylinder heads of the engine, a valve chamber housing to be cooled and defining the upper end of the engine and a crankcase with outer surfaces to be cooled, an engine-soundproofing encasing encompassing the outer surfaces of the engine and providing a cavity therewith, a first sound-absorbing coated housing built into the encasing of the engine and including an inlet for the cooling air, a second sound-absorbing coated housing built into the encasing of the engine and including an outlet for the cooling air, a distributing chamber, the entire cooling air supplied by the said blower being directed through the said cooling-air inlet into the said distributing chamber and from there in separate part currents over the said cylinder and cylinder head cooling surfaces and further elements of the engine requiring cooling, said valve chamber housing being located above the cylinder head of the engine, said cooling-air blower being laterally offset at the front end of the engine between said sound-absorbing coated housing including the cooling-air inlet and said distributing chamber, the latter extending alongside the sidewall of the crankcase closest to said cooling-air blower, separate cooling-air ducts branching off said distributing chamber, one of said cooling-air ducts leading from the distributing chamber to said cylinder and cylinder head cooling surfaces, a second cooling-air duct connecting the distributing chamber with said valve chamber housing, and at least one-third cooling-air duct leading from the distributing chamber to a sidewall of the crankcase opposite said distributing chamber.

2. An air-cooled internal combustion engine according to claim 1, the said soundproofing encasing covering also the underside of the said crankcase, a clearance between the said encasing and the said underside of the crankcase defining the said third cooling-air duct from the distributing chamber to the opposite sidewall of the crankcase.

3. An air-cooled internal combustion engine according to claim 1, comprising an oil sump defining a lower border wall of the said crankcase, the said soundproofing encasing covering also the said oil sump, a clearance between the said encasing and the said oil sump defining the said third cooling-air duct from the distributing chamber to the opposite sidewall of the crankcase.

4. An air-cooled internal combustion engine according to claim 1, comprising a connecting duct arranged inside the said .encasing in transverse relation on the crankcase sidewall closest to the said cooling-air blower and below the said cooling-air blower and defining the said third cooling-air duct from the distributing chamber to the opposite sidewall of the crankcase.

5. An air-cooled internal combustion engine according to claim 1, comprising a connecting duct inside the said encasing and arranged in transverse relation on the front end of the crankcase facing away from the said cooling-air blower and defining the said third cooling-air duct from the distributing chamber to the opposite sidewall of the crankcase.

6. An air-cooled, soundproof internal combustion engine comprising a cooling-air blower driven by a crankshaft, with cooling surfaces on the cylinders and cylinder heads of the engine, a valve chamber housing to be cooled and defining the upper end of the engine and a crankcase with outer surfaces to be cooled, and engine-soundproofing encasing encompassing the outer surfaces of the engine and providing a cavity therewith, a first sound-absorbing coated housing built into he encasing of the engine and including in inlet for the cooling air, a secondv sound-absorbing coated housing built into the casing of the engine and including an outlet for the cooling air, a distributing chamber, the entire cooling air supplied by said blower being directed through said cooling-air inlet into said distributing chamber and from there in separate part currents over said cylinder and cylinder head cooling surfaces and further elements of the engine requiring cooling, said coolingair blower being arranged at one extremity of said crankshaft, said sound-absorbing coated housing including said coolingair inlet located on the front end of the engine opposite said cooling-air blower, the cooling air being directed from said cooling-air inlet alongside the walls of the crankcase to the suction end of said cooling-air blower and from the delivery end of said cooling-air blower into said distributing chamber, the distributing chamber extending above said blower beside he cylinder and cylinder head of the engine, a first cooling-air duct branching off the distributing chamber to said cylinder and cylinder head cooling surfaces, and a second cooling-air duct connecting said distributing chamber with said valve chamber housing; 

1. An air-cooled, soundproof internal combustion engine comprising a cooling-air blower driven by a crankshaft, with cooling surfaces on the cylinders and cylinder heads of the engine, a valve chamber housing to be cooled and defining the upper end of the engine and a crankcase with outer surfaces to be cooled, an engine-soundproofing encasing encompassing the outer surfaces of the engine and providing a cavity therewith, a first sound-absorbing coated housing built into the encasing of the engine and including an inlet for the cooling air, a second sound-absorbing coated housing built into the encasing of the engine and including an outlet for the cooling air, a distributing chamber, the entire cooling air supplied by the said blower being directed through the said cooling-air inlet into the said distributing chamber and from there in separate part currents over the said cylinder and cylinder head cooling surfaces and further elements of the engine requiring cooling, said valve chamber housing being located above the cylinder head of the engine, said cooling-air blower being laterally offset at the front end of the engine between said sound-absorbing coated housing including the cooling-air inlet and said distributing chamber, the latter extending alongside the sidewall of the crankcase closest to said cooling-air blower, separate coolingair ducts branching off said distributing chamber, one of said cooling-air ducts leading from the distributing chamber to said cylinder and cylinder head cooling surfaces, a second cooling-air duct connecting the distributing chamber with said valve chamber housing, and at least one-third cooling-air duct leading from the distributing chamber to a sidewall of the crankcase opposite said distributing chamber.
 2. An air-cooled internal combustion engine according to claim 1, the said soundproofing encasing covering also the underside of the said crankcase, a clearance between the said encasing and the said underside of the crankcase defining the said third cooling-air duct from the distributing chamber to the opposite sidewall of the crankcase.
 3. An air-cooled internal combustion engine according to claim 1, comprising an oil sump defining a lower border wall of the said crankcase, the said soundproofing encasing covering also the said oil sump, a clearance between the said encasing and the said oil sump defining the said third cooling-air duct from the distributing chamber to the opposite sidewall of the crankcase.
 4. An air-cooled internal combustion engine according to claim 1, comprising a connecting duct arranged inside the said encasing in transverse relation on the crankcase sidewall closest to the said cooling-air blower and below the said cooling-air blower and defining the said third cooling-air duct from the distributing chamber to the opposite sidewall of the crankcase.
 5. An air-cooled internal combustion engine according to claim 1, comprising a connecting duct inside the said encasIng and arranged in transverse relation on the front end of the crankcase facing away from the said cooling-air blower and defining the said third cooling-air duct from the distributing chamber to the opposite sidewall of the crankcase.
 6. An air-cooled, soundproof internal combustion engine comprising a cooling-air blower driven by a crankshaft, with cooling surfaces on the cylinders and cylinder heads of the engine, a valve chamber housing to be cooled and defining the upper end of the engine and a crankcase with outer surfaces to be cooled, and engine-soundproofing encasing encompassing the outer surfaces of the engine and providing a cavity therewith, a first sound-absorbing coated housing built into he encasing of the engine and including in inlet for the cooling air, a second sound-absorbing coated housing built into the casing of the engine and including an outlet for the cooling air, a distributing chamber, the entire cooling air supplied by said blower being directed through said cooling-air inlet into said distributing chamber and from there in separate part currents over said cylinder and cylinder head cooling surfaces and further elements of the engine requiring cooling, said cooling-air blower being arranged at one extremity of said crankshaft, said sound-absorbing coated housing including said cooling-air inlet located on the front end of the engine opposite said cooling-air blower, the cooling air being directed from said cooling-air inlet alongside the walls of the crankcase to the suction end of said cooling-air blower and from the delivery end of said cooling-air blower into said distributing chamber, the distributing chamber extending above said blower beside he cylinder and cylinder head of the engine, a first cooling-air duct branching off the distributing chamber to said cylinder and cylinder head cooling surfaces, and a second cooling-air duct connecting said distributing chamber with said valve chamber housing. 